An electrical jack and header assembly has been proposed, wherein the jack comprises an insulating housing defining a cavity for receiving an electrical plug, and a row of electrical terminals secured to a wall of the cavity and each having a contact spring extending obliquely thereinto for engaging a respective electrical contact on the plug, and a contact tail depending from said wall, the header comprising an insulating block having secured thereto a row of contact elements each having on one side of the block a contact portion and on the opposite side of the block, a leg for insertion in a hole in a printed circuit board, the jack being matable with the header to cause each contact tail of the jack to engage a respective contact portion of the header. Such an assembly is appropriate to the telephone industry, where a telephone subscriber wishes to have an extra telephone point when such is needed. The telephone supplier assembles the header to the printed circuit board and installs it at the site of use. The subscriber mates the jack with the header when he needs said extra point.